Abstract Background Cutleaf geranium ( Geranium dissectum L) is a weed found in cereals and grasslands. Knowledge about the germination response of weeds under various environmental conditions is critical for their effective management, whereas such study has not been carried out thoroughly on this species. Objective This study was carried out to investigate the effect of some environmental factors on seed germination and emergence of cutleaf geranium. Methods The seeds were subjected to various environmental factors including water potentials, salinity, pH, high temperatures, burial depth and flooding at the temperature resulting in the highest germination (10 °C). All experiments were carried out twice, which were done consecutively. Results Germination percentage was halved at a water potential of -0.6 MPa, and no germination was observed at -2 MPa. Geranium dissectum seeds had negligible germination at 200 mM NaCl concentration. Seeds germinated over a pH range of 5-8, with the highest germination at pH between 6 and 7. Germination of this species reached from 85.0% after treatment at 80 °C but no seeds germinated after exposure to 120 °C. Maximum emergence was estimated 88.8%, which was halved at 2.2 cm depth. No emergence was observed at 4 cm or greater depths. Germination was 88.4% to 0% 15 days after flooding. Conclusions This species may not usually be found in areas with poor environmental conditions, and a semi-deep tillage or inclusion of rice in crop rotation may be used to control this weed.

Abstract Background Among the weeds in Iran, resistant Lolium rigidum Gaud is considered a troublesome weed in winter cereals due to its tendency to evolve cross (CR) and multiple resistance (MR) to herbicides. Objective This research examined the patterns and mechanisms of L. rigidum resistance to clodinafop-propargyl (CP) and mesosulfuron methyl+iodosulfuron methyl (MI). Methods Experiments were conducted on four putative-resistant L. rigidum biotypes and one susceptible biotype. The dose-response assay was performed on the biotypes with CP and MI. CR and MR were investigated with haloxyfop-R-methyl (HRM), sethoxydim (SD), pinoxaden (PN). and isoproturon+ diflufenican (ID) herbicides. An indirect study of the metabolism of herbicides was carried out using the cytochrome P450 monooxygenase (CYP450) inhibitors 1-aminobenzotriazole (ABT), piperonyl butoxide (PBO) and malathion. Finally, sequencing of ALS and ACCase genes was performed to investigate target-site resistance. Results All putative-resistant L. rigidum biotypes were resistant to CP, MI, and HRM, but susceptible to SD, PN, and ID. The indirect study showed that the P450 enzyme had no role in the evolution of resistance in L. rigidum biotypes. Resistance in this species was due to Ile-1781-Leu and Pro-197-Ser substitutions on ACCase and ALS encoding genes led to resistance, respectively. Conclusions Resistance in the studied L. rigidum biotypes to ALS and ACCase inhibiting was due of target site resistance. If these resistant biotypes are not controlled, they will become a problem for farmers in the region.

As pesquisas acerca do impacto da interferência das plantas daninhas sobre as culturas normalmente são realizadas com uma única espécie infestante, quando na realidade podem ocorrer diversas. Os objetivos deste trabalho foram avaliar a interferência de Brachiaria plantaginea e Ipomoea nil sobre o rendimento de grãos do feijoeiro (Phaseolus vulgaris) e determinar o nível de dano econômico (NDE) de cada espécie na cultura. Foram realizados dois experimentos a campo com as cultivares de feijão 'IPR Graúna' (Grupo Preto) e 'UTF-06' (Grupo Carioca) em convivência com infestações mistas em diferentes proporções aleatórias das espécies B. plantaginea e I. nil. Modelos de regressão múltiplos foram utilizados para determinar a capacidade de interferência de cada espécie daninha sobre a produtividade da cultura. O impacto de interferência de cada planta de I. nil correspondeu a 2,6 e 0,25 quando comparada a cada planta de B. plantaginea, dependente das proporções relativas na comunidade infestante e das condições de cada experimento. A cultivar 'IPR Graúna' apresentou maior habilidade competitiva do que 'UTF-06'. O NDE foi dependente da proporção relativa de cada espécie daninha na comunidade e foi obtido sob baixas infestações (<16 plantas m-2) em todas as condições testadas e simuladas.

The researches about the impact of weed interference on crops are usually performed with a single weed species, when in reality there are numerous. The objective of this study was to evaluate the interference of Brachiaria plantaginea and Ipomoea nil on the grain yield of French beans (Phaseolus vulgaris) and to determine the economic weed threshold (EWT) of each species on the crop. Two field experiments were conducted with bean cultivars 'IPR Graúna' (Black group) and 'UTF-06' (Carioca group) in coexistence with random proportions of mixed infestations of B. plantaginea and I. nil. Multiple regression models were used to determine the interference abi1lity of each weed species on crop productivity. The interference ability of each plant of I. nil corresponded to 2.6 and 0.25 of each B. plantaginea, dependent on the relative proportions on the weed community and on the conditions of each experiment. Cultivar 'IPR Graúna' showed higher competitive ability than 'UTF-06'. The EWT was dependent on the relative proportion of each weed species in the community and was reached under low infestation (<16 plants m-2) in all conditions tested and simulated.